Method for manufacturing transmittion bearing retainer

ABSTRACT

Disclosed is a method for manufacturing a transmission bearing retainer. The method includes a step of forming a bolt hole at the bearing retainer, wherein the bolt is inserted into the bolt hole. The step of forming the bolt hole includes: a step of forming a holt base hole of the bolt hole through piercing of a press working method; a step of forming an expanded hole through a first cold forging of the press working method, wherein a bolt head of the bolt being in contact with the expanded hole; and a step of forming anti-rotation grooves on a surface of the expanded hole through a second cold forging.

TECHNICAL FIELD

The invention relates to a method for manufacturing a transmission bearing retainer, more particularly, to a method for manufacturing a bearing retainer fixing a bearing supporting a shaft in a transmission so that the bearing does not move in an axis direction. In the method, dimensional accuracy of a portion where a bolt head of a bolt is coupled can be enhanced, and the bolt head of the bolt fixing the bearing retainer can be stably fastened to, close-contacted to, and assembled with the bearing retainer by minimizing a surface polishing process and maximizing a surface roughness. Accordingly, a formation of a gap at portion where the bolt head is in close contact, oil flow in the gap, vibrations of bolt, and a reduction of a fastening force can be effectively prevented.

BACKGROUND ART

A transmission is a device for matching running conditions by changing a reduction ratio of a vehicle engine. Various kinds of transmissions (such as a manual transmission, an automatic transmission, a continuously variable transmission) are being suggested. Typically, in a manual transmission 500 (a gear transmission) shown in FIG. 1, a gear 530 is installed in a case 510 to be assembled with each other.

Also, a shaft 520 is rotatably supported by a plurality of bearings 540 with respect to the case 510. In addition, oil is filled in the case 510 of the manual transmission 500. The oil reduces frictional heat generated during the operation and lubricates.

In this instance, the bearings in the transmission are supported by a bearing retainer and are installed so that movements of the bearings can be restricted.

With respect to the bearing retainer, “a bearing and a bearing retainer for a manual transmission” of Korean Publication Utility No. 20-0247094″ was suggested. A bearing supports a shaft in a transmission case, and a bearing retainer is fixed to the transmission case to restrict movements of the bearing in an axis direction. In this instance, protrusions laterally protruding are formed at an outer race of the bearing, and grooves where the protrusions are inserted are formed at the bearing retainer. An increase of durability of the bearing and an enhancement of the transmission are expected by preventing a rotation of the bearing.

In addition, “structure for preventing transmission oil inflow of clutch for vehicle” of Korean Patent Publication No. 0168287, “Mounting structure for bearing of manual transmission” of Korean Patent Publication No. 10-0423543, “Assembled structure of transmission bearing for vehicle” of Korean Utility Publication No. 20-0189152, “Bearing structure of automatic transmission” of Korean Utility Laid-Open Publication No. 1998-039714, and so on are suggested as technique related to the conventional bearing retainer.

FIGS. 2 and 3 are view for describing problems of the conventional bearing retainer.

In this instance, FIG. 2 is a view illustrating an example of a bearing retainer widely used for a manual transmission, and FIG. 3 is a view illustrating a cross section and a surface taken along a line A-A′ of FIG. 2.

Referring to FIGS. 2 and 3, the conventional bearing retainer 200 widely used for supporting a bearing in a transmission has an outer line 210 formed by considering an interference in other components, an auxiliary hole 220 where a component such as a pin is positioned, and bolt holes 230 where bolts are coupled.

In this instance, as shown in FIG. 2, the bolt hole 230 has an expanded hole 232 having an area larger than that of a bolt base hole 234 so that the bolt head can be positioned at the expanded hole 232. The expanded hole 232 is conventionally formed by a cutting work (such as milling, drilling and so on).

Therefore, in the conventional bearing retainer 200, a surface 236 of the expanded hole 232 of the bolt hole 230 has minute protrusions and/or identifications (or a concave-convex surface or an uneven surface) by tools used for the cutting working. Although a surface polishing process such as buffing is conventionally performed after machining, it is difficult to completely process the protrusions and/or identifications at the surface 236 of the expanded hole 232 formed during the cutting work due to limits of cost and time in the surface polishing process.

On the other hand, an environment that change physical properties of components positioned in the case of the transmission may be induced by the oil(transmission oil) filled in the transmission. For example, an environment that the components are oxidized may be induced. Therefore, plating or using an adhesive agent is restricted when the components used for the transmission are manufactured and assembled.

For such a reason as mentioned, in bearing retainer fixed to the case by a bolt in the case of the transmission, if there is a thin gap between contact surfaces of the bolt and the bearing retainer, the oil may be continually leaked, the bolt may be loosened, and a fatal defect may be generated (in the case that the bolt is loosened, the bearing may move and the bearing may be hung on a gear, thereby making the change of speed impossible).

That is, in the conventional bearing retainer 200 of the transmission, since it is difficult to completely eliminate the minute protrusions and/or identifications at the bolt hole 230 (specially, the expanded hole 232 that the bolt head is in close contact with) formed by the cutting working, it may cause the fatal defect of the transmission by the loosening of the bolt.

DETAILED DESCRIPTION Technical Problem to be Solved

Accordingly, the invention is for solving the above problems in the conventional art. The invention is directed to providing a method for manufacturing a transmission bearing retainer having a new shape so that a bolt head can be effectively fastened to and be in close contact with the bearing retainer during fastening the bolt by securing a surface roughness of a bolt hole (especially, an expanded hole where a bolt head is in close contact) stably.

Particularly, the invention is directed to providing a method for manufacturing a bearing retainer using a press working method instead of the conventional cutting working to form a bolt hole so that the bolt head of the bolt for fixing the bearing retainer can be effectively fastened to and in close contact with the bearing retainer by minimizing a surface polishing process and maximizing a surface roughness. Thus, a formation of a gap at portion where the bolt head is in close contact, oil flow in the gap, and loosening of the bolt can be effectively prevented.

In addition, the invention is directed to providing a method for manufacturing a bearing retainer being able to effectively prevent the loosening of the bolt by increasing a frictional force between the bolt head and the expanded hole through forming anti-rotation grooves at a surface of the expanded hole of the bolt hole.

The technical problems to be solved of the invention are not limited to the above technical problems to be solved. Other unmentioned technical problems to be solved of the invention can be clearly understood from the following descriptions by skilled person in the art to which the invention pertains.

Technical Solution

In a method for manufacturing a transmission bearing retainer in order to solve the above problems, the bearing retainer is fixed by a bolt so that a bearing for supporting a shaft does not move in ad axis in the transmission. The method includes a step of forming a bolt hole at the bearing retainer, wherein the bolt is inserted into the bolt hole. The step of forming the bolt hole includes: a step of forming a holt base hole of the bolt hole through piercing of a press working method; a step of forming an expanded hole through a first cold forging of the press working method, wherein a bolt head of the bolt being in contact with the expanded hole; and a step of forming anti-rotation grooves on a surface of the expanded hole through a second cold forging.

In the method for manufacturing a transmission bearing retainer, the step of forming the expanded hole and the step of forming the anti-rotation grooves may be performed after the step of forming the bolt base hole. The method may further include a step of reworking the bolt base hole through piercing of the press working method, after the step of forming the anti-rotation grooves.

The method for manufacturing a transmission bearing retainer may further include a step of forming an auxiliary hole for coupling to another component at the bearing retainer. The step for forming the auxiliary hole may be performed by the piercing of the press working method performed at the step of reworking the bolt base hole.

Advantageous Effect

In a method for manufacturing a transmission bearing retainer according to the invention, when a bolt hole of the bearing retainer where a bolt is coupled is formed, a bolt base hole 14 of the bolt hole is formed by piercing of a press working method, an expanded hole 16 where a bolt head of the bolt is in close contact is formed by cold forging (for example, sizing) of the press working method. Thus, a surface roughness of a portion (specifically, the expanded hole), where the bolt is coupled, formed through a plastic deformation is superior than the surface roughness of the portion formed through the conventional cutting working. Thus, dimensional accuracy of the portion where the bolt is coupled can be enhanced, and the bolt head of the bolt for fixing the bearing retainer can be fastened to and be in contact with the bearing retainer more stably by minimizing a surface polishing process and maximizing the surface roughness.

Therefore, a formation of a gap at the portion where the bolt head is close contact, oil flow in the gap, vibrations of the bolt, and failure and breakage that a fastening force of the bolt is reduced can be prevented.

In addition, a frictional force between the bolt head and the expanded hole can be increased by forming anti-rotation grooves at the surface of the expanded hole of the bolt hole. Accordingly, the loosening of the bolt can be prevented more effectively.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view illustrating a manual transmission according to an example.

FIG. 2 is a view illustrating an example of a bearing retainer widely used for a manual transmission.

FIG. 3 is a view illustrating a cross section and a surface taken along a line A-A′ of FIG. 2.

FIG. 4 is a flow chart for illustrating a method for manufacturing a transmission bearing retainer according to a preferred embodiment of the invention.

FIG. 5 sequentially illustrates the method for manufacturing the transmission bearing retainer according to the preferred embodiment of the invention.

FIG. 6 illustrates anti-rotation grooves of the transmission bearing retainer according to the preferred embodiment of the invention.

FIGS. 7 and 8 are SEM photographs for showing the contrast between surface roughness of the expanded holes of the transmission bearing retainers according to the conventional art and according to the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, preferred embodiments of the invention will be described with reference to FIGS. 4 to 8 of the accompanying drawings. Elements of FIGS. 4 to 8 acting same functions as the elements of FIGS. 1 to 3 have the same reference numerals.

Meanwhile, portions or elements that are known by the person skilled in the art (such as, an application and a structure of a bearing retainer, molds for blanking, piercing, cold forging, and so on(specifically, a progressive mold being able to be applied to a continuous working) used in a press working, press technique, various working methods for a surface polishing) are omitted in the drawings. Portions or elements related to the invention are shown in the drawings. Particularly, a size ratio between the elements may be different from an actual size ratio, and dimensions of the elements coupled to each other may be different. Since the differences in the drawings can be easily understood by the person skilled in the art, the detailed descriptions thereof will be omitted.

FIG. 4 is a flow chart for illustrating a method for manufacturing a transmission bearing retainer according to a preferred embodiment of the invention. FIG. 5 sequentially illustrates the method for manufacturing the transmission bearing retainer according to the preferred embodiment of the invention. FIG. 6 illustrates anti-rotation grooves of the transmission bearing retainer according to the preferred embodiment of the invention.

Referring to FIGS. 4 and 6, in the method for manufacturing the transmission bearing retainer according to the invention, a bearing retainer is manufactured by applying a press working method. The bearing retainer is fixed by a bolt so that a bearing supporting a shaft in the transmission cannot move in an axis direction.

Particularly, in the method for manufacturing the transmission bearing retainer according to the invention, when a bolt hole where the bolt is fastened is formed at the bearing retainer 10, a bolt base hole 14 of the bolt hole is formed by piercing of the press working method, and an expanded hole 16 that a bolt head of the bolt is in close contact with is formed by cold forging of the press working method. For example, the expanded hole 16 may be formed by sizing of the cold forging.

In the method for manufacturing the transmission bearing retainer according to the invention, the expanded hole 16 where the bolt head is coupled is formed through a plastic deformation of the press working method. Thus, the expanded hole 16 has an enhanced surface roughness, compared to the conventional expanded hole formed by a cutting work.

In this instance, in the preferred embodiment of the invention, a shape of the expanded hole 16 corresponds to a flat headed bolt (or flush bolt). Preferably, the expanded hole 16 may have a shape conventionally called counter sinking so that it corresponds to the flat headed bolt.

However, the shape of the expanded hole 16 may correspond to a bolt head of a used bolt.

Also, in the preferred embodiment of the invention, the bearing retainer 10 having the widely-used shape is shown in drawings. However, shapes of a main body 11 and an outer line 12 of the bearing retainer 10 may be varied.

In addition, in the embodiment, one auxiliary hole 18 is formed as an example. A number, a position, and a size of the auxiliary hole 18 may be set as necessary.

Referring to FIGS. 4 and 6 again, in the method for manufacturing the bearing retainer of the transmission according to the preferred embodiment of the invention, the main body 11, the bolt hole, and the auxiliary hole 18 are formed through a press working method (S100, S110, S120, S130), and then, the bearing retainer 10 is manufactured through a surface polishing process S140 and a heat-treating process S150. The bearing retainer 10 is fixed by a bolt so that the bearing supporting a shaft in the transmission cannot move in an axis direction.

In this instance, the main body 11 is formed by blanking of the press working method to have the predetermined outer line 12 of the bearing retainer 10 (S100).

Also, in the main body 11 of the bearing retainer 10, the bolt hole where the bolt is coupled is formed by the press working method. In the embodiment, the bolt base hole 14 of the bolt hole is formed by piercing of the press working method (S100), and then, the expanded hole 16 that the bolt head of the bolt is in close contact with is formed by reworking the bolt base hole 14 (S130).

In this instance, in the process of forming the bolt hole, a step S100 of forming the bolt base hole 14 of the bolt hole is performed in a step of forming the main body 11. That is, the blanking for forming the outer line 12 of the main body 11 and the piercing for the bolt base hole 14 are performed through a progressive mold or the like. The operation time can be decreased by using the progressive mold. A state that the bolt base hole 14 of the bolt hole is formed is shown in (a) of FIG. 5.

A first cold forging S110 of forming the expanded hole 16 and a second cold forging S120 of forming the anti-rotation grooves 160 at the expanded hole 16 may be performed by the progressive mold. However, in this case, a structure of the mold is complicate because a strength design of the mold is difficult, and a cost increases.

More particularly, the expanded hole 16 being in contact with a bottom surface of the bolt head is formed through the first cold forging, and the anti-rotation grooves 160 for preventing a rotation in a direction opposite to a direction fastening the bolt head are formed through the second cold forging. The anti-rotation grooves 160 are radially disposed on a surface of the expanded hole 16. Also, the anti-rotation groove 160 has inclines surfaces. An inclined angle of the inclined surface 161 exposed to the direction fastening the bolt head is larger than an inclined angle of the inclined surface 162 exposed to an opposite direction. Thereby, a frictional force by the anti-rotation grooves 160 is larger when the bolt head is loosened than when the bolt head is fastened. Accordingly, the loosening of the bolt head can be prevented. A state after the first cold forging and the second cold forging is shown in (b) of FIG. 5.

After forming the expanded hole 16 and the anti-rotation grooves 160 of the bolt hole, a reworking process (S130) of the bolt base hole 14 is performed through piercing of the press working method.

The reworking of the bolt base hole 14 is for eliminating the deformation of the bolt base hole 14 generated during the cold forging for forming the expanded hole 16. Dimensional accuracy of the bolt base hole 14 (especially, an interface with the expanded hole 16) can be increased. In the preferred embodiment of the invention, in the step of reworking the bolt base hole 14, the auxiliary hole 18 where another component is coupled is formed by the piercing of the press working method in the main body 11 of the bearing retainer 10. A state after reworking the bolt base hole 14 of the bolt hole is shown in (c) of FIG. 5.

Also, after forming the bolt hole and the auxiliary hole 18 at the main body 11 of the bearing retainer 10, a surface of the main body 11 of the bearing retainer 10 is polished by buffing, lapping, barrel, or the like (S140).

In addition, after polishing the surface of the main body 11 of the bearing retainer 10, the heat-treating process S150 of the bearing retainer 10 is performed. Thus, the bearing retainer 10 of a finished good having an increased surface hardness can be obtained. A state after the polishing and the heat-treating process is shown in (d) of FIG. 5.

FIGS. 7 and 8 are SEM photographs for showing the contrast between surface roughness of the expanded holes of the transmission bearing retainers according to the conventional art and according to the invention.

In this instance, (a) of FIG. 7 is a 50-times magnified photograph of the surface of the expanded hole of the transmission bearing retainer manufactured according to the preferred embodiment of the invention. (b) of FIG. 7 is a 50-times magnified photograph of the surface of the expanded hole of the transmission bearing retainer manufactured according to the conventional milling. (a) of FIG. 8 is a 200-times magnified photograph of the surface of the expanded hole of the transmission bearing retainer manufactured according to the preferred embodiment of the invention. (b) of FIG. 8 is a 200-times magnified photograph of the surface of the expanded hole of the transmission bearing retainer manufactured according to the conventional milling.

As shown in FIGS. 7 and 8, the bearing retainer 10 manufactured according to the preferred embodiment of the invention has an very enhanced surface roughness at the expanded hole 16 that the bolt for fixing is in close contact with.

The method for manufacturing the transmission bearing retainer according to the preferred embodiment of the invention is described in the detailed descriptions and is shown in the accompanying drawings. However, it is just an example. Accordingly, the skilled person in the art can understand that various modifications of the embodiments are possible within the scope having technical features of the invention.

Thus, various modifications of the embodiments are possible by those person in the art within the scope having the technical feature of the invention. The scope of the invention is defined by the appended claims.

DESCRIPTIONS OF REFERENCE NUMERALS

-   -   10: a bearing retainer     -   11: a main body     -   12: an outer line     -   14: a base hole     -   16: an expanded hole     -   18: an auxiliary hole     -   160: anti-rotation grooves 

1. A method for manufacturing a transmission bearing retainer, wherein the bearing retainer fixed by a bolt so that a bearing for supporting a shaft does not move in ad axis in the transmission, comprising: a step of forming a bolt hole at the bearing retainer, wherein the bolt is inserted into the bolt hole, wherein the step of forming the bolt hole comprises: a step of forming a holt base hole of the bolt hole through piercing of a press working method; a step of forming an expanded hole through a first cold forging of the press working method, wherein a bolt head of the bolt being in contact with the expanded hole; and a step of forming anti-rotation grooves on a surface of the expanded hole through a second cold forging.
 2. The method according to claim 1, wherein the step of forming the expanded hole and the step of forming the anti-rotation grooves are performed after the step of forming the bolt base hole, wherein the method further comprises a step of reworking the bolt base hole through piercing of the press working method, after the step of forming the anti-rotation grooves.
 3. The method according to claim 2, further comprising: a step of forming an auxiliary hole for coupling to another component at the bearing retainer, wherein the step for forming the auxiliary hole is performed by the piercing of the press working method performed at the step of reworking the bolt base hole. 